engine miss in an old 89 sp, 580

[Gene575]

I have a pair of these for the kids and one has developed an engine miss under load. The history of the ski is, rebuilt carb. w/needle and seat, good fuel pump pressure (old sytle seperate pump),new plugs (a couple of time over),and just this weekend a set of new spark plug caps(wishfull thinking, and easy to replace). I can pull the choke to check for a lean miss condition, and it goes to no power won't run. So I'm pretty sure it's not fuel related. Plugs are also a nice chocolate brown. Idles fine and seems ok for the first few minutes of operation. What would you recommend I do next? I can just start replacing parts, but would like replace one part and have it fix the problem. thanks in advance

[Bryan Glynn]

Did you snip off some plug wire when you replace the boots? If not try that first. I would try the coils next.

[Gene575]

I failed to mention on more symtom. When it is running under wot, there is a vibration or moaning noise coming from the engine area. I thought maybe a driveshaft bearing,(because on a recent impeller change I noticed slight wear) but now wondering if it's the crank! I have heard on another message board, that crank bearing can cause similar problems. What do you think? And if so, can a person just replace, say the bearing that is bad, or do all the bearing get replaced, as a matter of service.

[Bryan Glynn]

If you are hearing noises from your engine, STOP RUNNING it until you get it repaired, unless you want to risk blowing it up and costing you double in part replacement costs! Why would you spend the time and money to tear it down and rebuild it, and not replace all the bearings? That's assuming it's an end bearing in the first place...

[Gene575]

Thanks, Bryan and just to confirm before I give the engine the hook this morning. You agree that there is crankshaft problems? The noise was only evident when at or near wot. I don't ride the ski, so I don't know how long it had been making the noise. And a perfect description on the noise is an electric engraving tool. And you can hear it over the exhaust, almost like it's coming from the water. Give it the hook then?

p.s could this also be the cause of the engine miss?

[Bryan Glynn]

It's probably not causing a miss, unless the crank has twisted - ride withthe seat off and verify it's actually coming from the engine, but what you are describing is a bad bearing. If it's in the engine, it needs to be fixed ASAP.